CRL M66 is a one-part, moisture curing, gun grade modified polyurethane sealant. It does not require a primer on most common construction surfaces. CRL M66 is durable, flexible, and offers excellent performance in moving joints.

Basic Uses CRL M66 Modified Polyurethane Construction Sealant is specially formulated to outperform traditional VOC solvent polyurethanes for sealing moving joints in concrete, masonry, metal, and other basic perimeter joint applications. It is ideal for all joints between framing (door and window) and the building structure in both storefront and curtain wall applications to secure a watertight installation. This advanced polymer formula offers excellent adhesion to fluoropolymer paint coatings for metal surfaces including KYNAR®, Duranar®, and Duranar® Sunstorm® Coatings, as well as standard metal, aluminum, steel, galvanized steel, plastics, vinyl, glass, wood, concrete, brass, and other common building substrates.

CRL M66 is compatible with insulating glass sealants when glazing units and applied as a toe or heel bead. CRL M66 is designed for exterior and interior use. Withstands temperatures after full cure from -75°F to 300°F (-59 to 149°C). Paintable after only two hours with water-based paints.

The light grainy texture has proven very popular for matching textured substrates like stucco and masonry, and for smooth metal storefront joints where the light texture blends and hides tooling marks and the wavy effect that is inevitable when tooling sealants.

It is also suitable for varied manufacturing uses, such as the production of travel trailers and mobile homes, and in the assembly of galvanized air conditioning ductwork.

Low temperature gunning and application above 0°F (18°C). Service temperature of -75°F to 300°F (-59°C to 149°C). Permanently Flexible – Will not get hard with age like traditional polyurethanes. Remains flexible in low temperatures.

Fast Cure - Skins over in 30 minutes and continues to cure at a rate of 1/8" (3 mm) depth per day.

Tooling time – approximately 20-40 minutes, depending on temperature and humidity.

Limitations Do not apply over damp or contaminated surfaces. Use with adequate ventilation. Not recommended for surfaces with special protective or cosmetic coatings without prior consultation of the manufacturer. Should not be applied to mirrors or unpredictable absorptive surfaces such as marble, limestone or granite unless a standard of appearance has been agreed on as a result of testing for stain and/or discoloration. Check cartridge label, MSDS, and Specification Data Sheet for additional limitations.

Comparable SealantsCRL: M64 Modified Polyurethane Sealant, M65W PermaWhite. Tremco®: Vulkem® 116, Vulkem 921, DyMonic®, DyMonic® FC, TremGlaze U1400, TremPro 626. Sika®: 1A, 15LM. Sonneborn®: NP1. Pecora®: Dynatrol 1. OSI®: PR-255. Schnee Moorehead: 7100 Sealant. Bostik: Chem-Caulk 900. Important Notes: Do not apply over damp or contaminated surfaces. Use with adequate ventilation. Not recommended for surfaces with special protective or cosmetic coatings without prior consultation of the manufacturer. Should not be applied to mirrors or unpredictable absorptive surfaces such as marble, limestone or granite unless a standard of appearance has been agreed on as a result of testing for stain and/or discoloration. Check cartridge label, MSDS, and Specification Data Sheet for additional limitations.